Analyzed 09Z Thu Aug 24, 2017
Valid 12Z Thu Aug 24, 2017
Valid 18Z Thu Aug 24, 2017
Valid 00Z Fri Aug 25, 2017
Valid 06Z Fri Aug 25, 2017
Valid 12Z Fri Aug 25, 2017
Valid 00Z Sat Aug 26, 2017
Valid 12Z Sat Aug 26, 2017
Valid 12Z Sun Aug 27, 2017
Valid 12Z Mon Aug 28, 2017
Valid 12Z Tue Aug 29, 2017
Valid 12Z Wed Aug 30, 2017
Valid 12Z Thu Aug 31, 2017
+ Short Range Forecast Discussion (Day ½-2½)
+ Medium Range Forecast Discussion (Day 3-7)
Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
434 AM EDT Thu Aug 24 2017
Valid 12Z Thu Aug 24 2017 - 12Z Sat Aug 26 2017
...Tropical Storm Harvey continue to strengthen while bringing
heavy rainfall in Texas by Friday...
...Heavy rainfall expected across South Florida...
...Thunderstorms will continue across the Southern Rockies...
The National Hurricane Center currently has Tropical Storm Harvey
in the western Gulf of Mexico. Harvey will take a northwestward
track as it moves toward the Middle Texas coast while
strengthening into a category 1 hurricane sometime Friday morning.
Precipitation will begin to approach Deep South Texas by Friday
morning--with heavier bands moving from the Middle Texas coast and
Deep South Texas by Friday evening. By Saturday morning, Harvey
will weaken to a tropical storm once again. However, the heavy
rainfall will increase over the Middle Texas coast and will
continue beyond the short term period. With Harvey moving slowly
as it approaches Texas and after it makes landfall, this may give
way to the potential of bringing an extreme amount of rainfall to
both Deep South Texas and Southeast Texas. Flash flooding will be
a threat because of this. Thus, continue monitoring both the
National Hurricane Center for the official track and intensity of
Harvey in addition to WPC for rainfall amounts and regions of
An inverted trough will interact with deep moisture across the
southern half of Florida over the next few days. This will bring
showers and thunderstorms that could produce heavy
rainfall--primarily in South Florida. Thunderstorm activity will
ramp up by this afternoon and continue across South Florida
through Thursday night and into Friday morning. By Friday
afternoon, a cold front will begin pressing southward over central
Florida which will aid in the continuation of thunderstorms
leading into the weekend.
A wavy front along the central and western Gulf Coast region will
stall along these areas by this afternoon and stays put through
Saturday. This boundary will act as a focal point for setting off
convection across these coastal areas. The boundary will also
stall across the Carolinas, which will bring heavy rainfall to
coastal areas of those states. However, by early Friday morning,
the front will begin to move offshore. As a result, most of the
precipitation will also move off into the Atlantic.
With an upper-level trough coming in from the west and sufficient
moisture in place, the Southern Rockies can expect showers and
thunderstorms over the next few days. A slight risk of flash
flooding for this region will be in place as some of these
thunderstorms will be capable of producing heavy downpours.
Farther north, a cold front will move across the Pacific Northwest
and Northern Rockies on Thursday--bringing light showers to these
regions. As the front sweeps across the Northern High Plains,
showers and thunderstorms will develop ahead of the front and will
spread across the northern Plains in addition to the Upper Midwest
Graphics available at
+ Additional Links
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
222 AM EDT THU AUG 24 2017
VALID 12Z SUN AUG 27 2017 - 12Z THU AUG 31 2017
...EXTREMELY HEAVY RAIN POSSIBLE ALONG THE NW GULF COAST THIS NEXT
UPPER RIDGING IS FORECAST TO LINGER ACROSS THE WESTERN US,
SUPPORTING TROUGHING IN THE MID-MISSISSIPPI AND OHIO VALLEYS. IN
THE GULF OF MEXICO, THE NATIONAL HURRICANE CENTER IS WRITING
ADVISORIES ON TROPICAL STORM HARVEY WITH A TRACK AIMED TOWARD THE
TEXAS COAST. PLEASE CONSULT THE LATEST NHC FORECAST FOR DETAILS.
SERIOUS FLOODING IS A DISTINCT POSSIBILITY OVER SOUTHEASTERN TEXAS
INTO LOUISIANA NEXT WEEK AS HARVEY MAY VERY SLOWLY WOBBLE BETWEEN
THE COAST AND THE GULF OF MEXICO BEFORE POSSIBLY BEING PICKED UP
BY THE TROUGH TO THE NORTH.
DETERMINISTIC GUIDANCE CONTINUED TO WAVER A BIT ON THE TRACK OF
HARVEY, DEPENDING ON THE UPPER FLOW AND SUBTLE DETAIL DIFFERENCES.
NHC ADJUSTED THE TRACK AT 03Z TO A HALF CYCLONIC LOOP NEAR CORPUS
CHRISTI PER THE 12Z GFS/ECMWF AND ENSEMBLE GUIDANCE. USED THOSE
MODELS WITH THE 12Z ECMWF ENSEMBLE MEAN TO FORM THE FORECAST.
FARTHER NORTH, THE IMPORTANT SHAPE/AMPLITUDE OF THE TROUGH WAS
MOST CONSISTENTLY DEPICTED BY THE ECMWF ENSEMBLE MEAN WHICH HAS
TRENDED SHARPER IN THE RIDGE/TROUGH CONFIGURATION, BUT PERHAPS NOT
SW ENOUGH TO PICK UP HARVEY BEFORE LATER NEXT WEEK. 12Z GFS
APPEARED TO BE MOST REASONABLE BY NEXT WED/THU, LIFTING HARVEY
NORTHWARD ACROSS LOUISIANA SLOWER THAN THE 12Z ECMWF (GIVEN THE
BACK TO THE NORTH AND WEST, ECMWF ENSEMBLES BACKED OFF ON LOWERING
HEIGHTS AS MUCH INTO THE PAC NW TUE/WED (GEFS HAD THAT IDEA 24 HRS
AGO) DUE IN PART TO THE STRONGER RIDGE IN THE INTERIOR. 50/50
SPLIT BETWEEN THE 12Z GFS AND ECMWF ENSEMBLE MEAN ROUNDED OUT THE
FORECAST FOR NEXT THURSDAY.
SENSIBLE WEATHER HIGHLIGHTS
EXPECT SHOWERS AND THUNDERSTORMS TO FOCUS ACROSS THE SOUTHEAST AND
THE GULF COASTS ALONG A LINGERING STATIONARY FRONTAL BOUNDARY.
FLORIDA AND THE SOUTHEAST COAST SHOULD ALSO SEE AN INCREASE IN
RAINFALL AS A TROPICAL WAVE INTERACTS WITH THIS FRONTAL BOUNDARY
TO PRODUCE A SFC WAVE THAT SLOWLY MOVES OFFSHORE THE SOUTHEAST AND
MOISTURE FROM THE FRINGE OF HARVEY ROTATE INTO THE REGION. TO THE
NORTH, SHOWERS AND THUNDERSTORMS WILL DEVELOP ACROSS THE CENTRAL
U.S. AND THE NORTHERN PLAINS/UPPER MIDWEST AHEAD OF UPPER
TROUGHING AND A WEAKENING SFC COLD FRONT. AFTERNOON SHOWERS AND
THUNDERSTORMS SHOULD ALSO DEVELOP ACROSS THE CENTRAL/SOUTHERN
ROCKIES (CO/NM PRIMARILY) JUST TO THE EAST OF THE UPPER HIGH.
THE WEST WILL SEE WARMER THAN AVERAGE TEMPERATURES WITH RECORD
HIGHS POSSIBLE IN THE INTERIOR NW. BELOW AVERAGE TEMPERATURES ARE
EXPECTED OVER MUCH OF THE CENTRAL/EASTERN STATES, ESPECIALLY IN SE
TEXAS INTO LOUISIANA GIVEN AN EXPANSIVE RAIN SHIELD.